Storage virtualization is known as a technique for centrally managing storage volumes of multiple storage devices included in a system as virtual volumes. According to the storage virtualization technique, arbitrary areas carved from multiple volumes in storage devices are defined as virtual volumes. Such virtual volumes provide a host system (an upper system) or the like requesting storage resources with a requested storage capacity at a requested time.
In the following, such virtual volumes will be described with reference to FIG. 15. FIG. 15 illustrates a conventional system for providing virtual volumes to host systems.
The system illustrated in FIG. 15 includes a plurality of storage devices 200 (200a to 200d), a plurality of host systems 300 (300a to 300c), and a plurality of virtualization devices connected between the storage devices 200 and the host systems 300. In such a system (hereinafter referred to as a virtualized system), a virtual switch 100 registers storage volumes of the storage devices 200a to 200d as LUNs (logical unit numbers) 201a to 201g. Further, the virtual switch 100 provides the host systems 300a to 300c with these LUNs 201a to 201g as virtual volumes (VLUN (virtual logical unit numbers)) 301a to 301c, respectively, each having a specified capacity. This causes each of the host systems 300a to 300c to recognize the storage volumes configured with the multiple LUNs as a single volume. Data written to the virtual volumes are substantially written to the storage volumes of the storage devices that constitute the virtual volumes.
According to the system described above, when the capacity of each of the storage devices is 1 Tbyte, and the capacity requested by one of the host systems is 1.5 Tbytes, it does not need to allocate two or more storage devices to the host system. In this case, the virtual switch combines three 0.5-Tbyte LUNs to be provided to the host system as one volume of 1.5 Tbytes.
Techniques related to the technique which will be discussed include a data processing system, a data processing method, and a storage apparatus. According to the system, when a failure occurs in a part of a plurality of first memory areas and there is no spare second memory area to migrate data in the faulty part of the first memory areas, another part of the first memory areas is dynamically reserved as a second memory area. There is Japanese Laid-open Patent Publication No. 2008-009767 as a reference document.
However, in order to overcome degradation of storage devices in such a virtualized system as illustrated in FIG. 15, hot spare storage devices may be prepared for the individual storage devices to maintain redundancy. That is, when the scale of the virtualization system increases, the number of storage devices increases. Proportionally to the increase in the number of storage devices, the number of requested hot spare storage devices also increases. In addition, the storage capacity of a hot spare storage device needs to be larger than that of a corresponding storage device. Thus, the amount of storage resources that may not be effectively used increases with increasing capacity of each storage device in a virtualized system.